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China's great flood really happened, say geologists

Sediments in Yellow River gorge support oral histories that go back to the founding of Chinese civilisation. Bill Condie reports.

Jishi Gorge upstream the landslide dam. The grey silt deposits dozens of metres above the water level are lacustrine sediments.

Wu Qinglong

According to legend, a great flood engulfed China more than 4,000 years ago, when a landslide dammed the Yellow River in Jishi Gorge.

The waters from this catastrophe were only controlled when Emperor Yu, according to some accounts, cut through a mountain ridge with a divine battle-axe.

These massive engineering feats established the first Chinese dynasty, according to oral tradition.

Geologists now say the flood part of the legend at least is true, although they place the event at about 1,900 BCE.

By studying sediments high up the sides of Jishi Gorge, in the Yellow River, scientists found evidence of a huge dam that blocked the pass for six to nine months. When it burst, it unleashed 16 cubic kilometres of water downstream.

Wu Qinglong of Nanjing State University, lead author of a study published in Science, and his colleagues stumbled on the sediments from the ancient dam in 2007.

“It inspired us to connect the next possible outburst flood with the abandonment of the prehistoric Lajia site 25 kilometres downstream,” he told journalists in a teleconference.

“But at that time we had no idea what the evidence of a catastrophic outburst flood should be.

“In July 2008 I suddenly realised that the so-called black sand previously revealed by archaeologists at the Lajia site could be, in fact, the deposits from our outburst flood.”

Wu and his colleagues also found evidence of an earthquake that allowed them to come up with a likely timeline.

They believe the earthquake triggered the landslide that blocked the river, leading to the build-up of a lake some 200 metres deep.

The dam then broke, causing catastrophe downstream.

The variable timelines for the start of the Xia dynasty according to traditional Chinese culture, the Xia-Shang-Zhou Chronology Project and the flood that was newly identified and dated by Wu et al.

Carla Schaffer/AAAS

Details of the achievements of Emperor Yu, also known as Yu the Great, are hard to verify as they occurred before written records.

But the stories say he devised a system of flood controls that were crucial to establishing Chinese civilisation.

Yu is said to have created a system of irrigation canals to divert floodwater into fields, in a massive project that took 13 years to complete.